1. Field of the Invention
The present invention relates to the production of oil and natural gas. More particularly, this disclosure relates to methods for controlling the concomitant production of undesirable fluids such as water from oil and gas-bearing reservoirs, and to repair and seal pipes in production or injection wells, pipelines, and utility conduits.
2. Background of the Invention.
This disclosure relates to the production of oil and natural gas. More particularly, this disclosure relates to methods for controlling the concomitant production of undesirable fluids such as water from oil and gas-bearing reservoirs. Such produced water can be reservoir water, occasioned by coning or such similar phenomena of the aquifer or it can be injection water from secondary recovery treatments being applied to the reservoir. Whatever the source, there is an upper limit beyond which water production can no longer be tolerated and its further entry into the producing well bore must be at least reduced if further production of the hydrocarbon resources at that location is to be continued.
Regardless of whether the undesired fluid is a natural drive fluid (e.g. water) or an artificial drive fluid (e.g., from secondary recovery liquid or gas projects, gas repressurization, miscible displacement projects, etc.), the problem is primarily occasioned by the predilection of the natural or artificial drive fluid to preferentially seek the higher permeability zone and to more or less bypass the lower permeability zones.
Among the prior solutions to the problem of undesirable fluid entry is the placing or forming of a plug within the formation. At one time such plugs were of a solid nature, such as cement, regardless of whether the undesirable fluids were liquid or gas. Such solid plugs, while at least partially effective for the intended purpose, inhibit the use of the undesirable fluid to assist in driving the desired fluid from the formation into the producing well bore. In addition, the use of such solid plugs invariably results in the permanent loss of desired fluids. Further, should the undesirable fluids seep around or otherwise bypass such solid plugs, the plug cannot change or shift position to block such seepage or other changes in flow pattern of the undesired fluid.
To overcome the shortcomings of the use of solid plugs such as cement, there was developed the concept of modifying the mobility of fluids present in the subterranean formations. Such methods have generally been directed to modifying the mobility of the hydrocarbon displacing liquid medium. The mobility of any fluid in a permeable geological formation is the effective permeability of the formation to that liquid divided by the viscosity of the fluid. Thus, a commonly developed method for reducing the mobility of a particular fluid in a permeable geological formation is to increase its viscosity such as by using viscous solutions of partially hydrolyzed polyacrylamides such as described by Sandiford et al in U.S. Pat. No. 2,827,964 and McKennon U.S. Pat. No. 3,039,529.
A serious problem in the secondary recovery of oil from oil bearing or containing subterranean formations, wherein a fluid such as water is injected into the formation via one or more injection wells to drive the oil through the formation to one or more production wells, is the development of high permeability flow zones. These high permeability flow zone are known as “thief” zones and permit the drive fluid to channel directly from the injection well to the production well. In many instances, the channeling or fingering resulting from the injection well to the production well results in a low volumetric sweep efficiency. Substantial quantities of oil are left in the less permeable zones of the formation, which are bypassed in the process. Induced fractures are often the result of over-pressuring the formation at some point. In other instances, water breakthrough may be related to permeability contrasts between different layers, which may or may not be in vertical communication in the reservoir. Permeability modification treatments help improve volumetric sweep efficiency. In waterfloods, injection-well treatments are most common.
What is needed is a system and method for addressing the above, and related, issues.